460 infusoria: — encysting process; metamorphosis. 



body (b) appears to break up (c, d) into numerous gemmules, 

 which are analogous to the ' zoospores' of Protophytes, and which, 

 like them, are set free by the bursting of the parent-cyst (e), swim- 

 ming forth to develope themselves into new individuals of the same 

 kind, though at first, perhaps, bearing little or no resemblance to 

 the type from which they sprang. 



345. In Trichoda lynceus, on the other hand, the Encysting 

 process appears subservient to a kind of Metamorphosis of the 

 individual (like the somewhat parallel passage of Insects through 

 the pupa-stage) ; the Animalcule which emerges from the 

 cyst having characters in many respects different from those 

 of the Animalcule which became encysted, but no multiplication 

 being effected either by subdivision or gemmation. According 

 to M. Jules Haime, by whom this history was very carefully 

 studied, * the form to be considered as the Larval one is that 

 shown in Fig 242, A — e, which has been described by Prof.Ehren- 

 berg under the name of Oxytricha. This possesses a long, narrow, 

 flattened body, furnished with cilia along the greater part of both 

 margins, and having also at its two extremities a set of larger and 

 stronger hair-like filaments ; and its mouth, which is an oblique 

 slit on the right-hand side of its fore-part, has a fringe of minute 

 cilia on each lip. Through this mouth, large particles are not 

 unfrequently swallowed, which are seen lying in the midst of the 

 gelatinous contents of the general cavity of the body, without any 

 surrounding ' vacuole ; ' and sometimes even an Animalcule of 

 the same species, but in a different stage of its life, is seen in the 

 interior of one of these voracious little devourers (b). In this 

 phase of its existence, the Trichoda undergoes multiplication by 

 transverse fission, after the ordinary mode (c, d) ; and it is usu- 

 ally one of the short-bodied ' doubles ' thus produced (e) that 

 passes into the next phase. This phase consists in the assumption 

 of the globular form, and the almost entire loss of the locomotive 

 appendages (f) ; in the escape of successive portions of the gra- 

 nular sarcode, so that s vacuoles ' make their appearance (g) ; and 

 in the formation of a gelatinous envelope or cyst, which, at first 

 soft, afterwards acquires increased firmness (h). After remaining 

 for some time in this condition, the contents of the cyst become 

 clearly separated from their envelope ; and a space appears on one 

 side, in which ciliary movement can be distinguished (i). This 

 space gradually extends all round, and a further discharge of 

 granular matter takes-place from the cyst, by which its form 

 becomes altered (k) ; and the distinction between the newly-formed 

 body to which the cilia belong, and the effete residue of the old, 

 becomes more and more apparent (l). The former increases in 

 size, whilst the latter diminishes ; and at last the former makes 

 its escape through an aperture in the wall of the cyst, a part of 



* "Annales des Sci. N at." Ser. 3, Tom. xix. p. 109. 



